But within 24 hours of its lengthy puff announcing its serialisation the paper ran a leading article explaining that it had changed its mind.

The decision followed the jamming of its switchboard as hundreds of Rangers fans called to complain while others took to Twitter. Rangers itself lobbied the paper and threatened to ban Sun journalists from its ground. There were also physical threats made to The Sun reporter who wrote the interview with Mac Giolla Bhain.

Before I unravel this remarkable tale, I must declare an interest. I read a draft of the book and provided an approving quote that appears on the back cover.

The story stretches back four years. Mac Giolla Bhain was the first journalist, and, for much of the time, the only journalist, to chart the financial dramas that led to the demise of Rangers football club.

The fact that he worked outside the Scottish media establishment to tell the twists and turns of the tale in a blog is hugely relevant. Indeed, a crucial part of the story involves the initial failure of Scotland's journalists to investigate the internal shenanigans at Rangers.

For his trouble, Mac Giolla Bhain suffered from persistent verbal threats from people calling themselves Rangers fans. As his name suggests, he is Irish, though he was born and raised in Scotland. He moved to Donegal in the Irish republic 15 years ago.

Once Rangers went into liquidation in February this year, it was natural that Mac Giolla Bhain was selected by a publisher - Bob Smith of Frontline Noir - to write about the scandal. Ironically, it was a Sun staffer who originally recommended Mac Giolla Bhain to Smith as the possible author of a book about a different topic.

Mac Giolla Bhain was well known to The Sun, having previously freelanced for the its now-defunct stablemate, the News of the World, and having a high profile in Scotland due to his blog.

The Sun's Scottish editor, Andy Harries, admired Mac Giolla Bhain's work and, on hearing about his book, made a swift decision to buy the serialisation.

He planned to run two successive spreads and one of his staff, Simon Houston, was assigned to interview Mac Giolla Bhain. The result, as shown in this screen-grab before it was taken down from the paper's website, was hugely sympathetic to the blogger.

It stated that he had broken "one of the biggest stories in Scottish football history" and revealed that he had been the "target of sectarian hate from extremists" and had been subject to "sinister death threats" which had "left his family living in fear."

The article, announcing the book's serialisation, predicted that it would "shoot straight to the top of the Scottish bestsellers list, with pre-sale orders already through the roof."

It described Mac Giolla Bhain as "an internet phenomenon" who, in May 2010, handed the News of the World "the story which rocked Scottish football by revealing that the taxman sent Rangers a demand for a staggering £24m... one of a string of predictions Mac Giolla Bhain made about the Glasgow giants' perilous financial state which came to fruition."

Within hours of publication, Rangers fans - or people who call themselves fans - began calling the paper and tweeting. Evidently, some of them mentioned a controversial posting by Mac Giolla Bhain on his blog in April this year.

Headlined The Incubator, it was a satire on the bigotry of many Rangers' fans. In so doing, it employed obviously offensive images.

Harries and some of his senior staff were said to have been alarmed by the blog's implications. In a rapid about-turn, Harries decided to pull the serialisation despite the puff promising to run it.

We knew Mac Giiolla Bhain was "a controversial figure", it said, but "it was clear from the book he had written that he had a story to tell. And we felt it was a story that needed to be told to you, so that you could make your own minds up. So that you had a chance to read the behind-the-scenes details about the downfall of Rangers. So that you had a chance to see where the blame lay for the collapse of the club."

But it went on to argue that Mac Giolla Bhain's single blog posting "undermines the entire industry" and that was the reason to cancel the serialisation of his book

It stressed that the decision was "NOT because of the social media backlash" and "NOT because of the internet bullies... but because the author — previously unbeknown to us — is tarred with a sickening sectarian brush."

The leader continued: "We believed Phil Mac Giolla Bhain to be a proper and sound journalist. Channel 4 News chief correspondent Alex Thomson obviously agreed and wrote the foreword in the book. He was wrong and so were we."

I called Harries, who refused to comment further, simply saying: "I stand by what I wrote in my leader."

Given my belief in the credibility of the book and Mac Giolla Bhain, I took wide counsel on the affair from those who support him and those who do not, and from staff at the Scottish Sun.

The general consensus is that Harries made a bad call initially by agreeing to serialise a book that was bound to upset Rangers fans. (I understand that the cancellation has resulted in scores of calls and complaints from rival Celtic fans throughout the day).

But Harries, though English, has been in Glasgow for 25 years and is said to understand the sensibilities in a city divided by football and faith. I understand that he still believes in the book's authenticity.

One of his senior staff told me that he was "devastated" on reading Mac Giolla Bhain's "incubator" blog posting and felt he was in an impossible position.

But two experienced non-Sun journalists, both of whom did not favour serialisation, read the situation differently. They believe Harries was shocked by the hostility of Rangers fans and feared a possible sales boycott not unlike the one that the paper suffered after its infamous accusation against Liverpool fans following the 1989 Hillsborough tragedy.

He was therefore relieved to find an excuse - the blog posting - in order to effect a change of direction.

That view is strenuously denied by Harries's senior colleagues. They say he is genuinely heartbroken at the turn of events. He felt he couldn't "defend the indefensible" (Mac Giolla Bhain's blog) by facing down complaints from Rangers' fans.

"He found himself in an impossible position," said one. "He just felt he couldn't justify going ahead." Naturally enough, Mac Giolla Bhain is furious too. He believes his April blog posting was so obviously satirical that Harries has used it to get himself off the hook. Several journalists agree with him.

He said: "I think this is a dark day for journalism in Scotland when a major title can be forced into self-censoring in this fashion.

"The most worrying aspect of this are the threats aimed at Simon Houston who interviewed me. An attack on a journalist is an attack on journalism and, ipso facto, an attack on democracy."